This is a question I briefly pondered during our kitchen remodel. Now that we (Jen) are starting to get into gardening, we will likely get a composting bin, which we'll do once this record-setting winter finally passes over Chicago. But gutting our kitchen gave us the opportunity to get a garbage disposal too.
During the deliberations, I noticed an overstock In-Sink-Erator came up on eBay a few months ago, I splurged for it (and was later told by the plumber that I got a good deal on it). Now that it is installed, a few times I have flipped the switch and wondered how it impacted the enviornment.
Well one of my news feeds recently carried an article by the WSJ about this topic. At first, I was surprised to hear that some countries (UK, Japan, Australia) actually had legislation prohibiting the installation of garbage disposals. I was even more surprised that many are now repealing those laws and encouraging people to install these in their homes to help deal with the issues they're running into with solid waste management.
There is also an good overview of the environmental pros and cons of disposals:
Pluses: "Carting organic waste to landfills contributes to several problems. It requires using garbage trucks, which spew pollutants. In addition, mixing food waste into garbage can make it more difficult for sanitation workers to sort out recyclables, and more energy is required to incinerate the water-laden refuse. And most importantly, landfills themselves produce a lot of methane, a potent greenhouse gas."Most interesting to me was that the USGBC is considering awarding LEED points to homes with a garbage disposal. There is even some really advanced Swedish engineering that separates solids from water after the disposal has done its duty, and then takes the solid waste and uses it to create methane, effectively turning waste into energy!
Minuses: "Sending food waste through a kitchen garbage disposal, however, creates a different set of headaches. It increases water usage slightly, according to several studies. Engineers worry that as the waste passes through municipal sewer systems to treatment plants, the ground-up food sometimes contributes to clogging. And after treating the waste-water, plants are left with more sludge, which is costly to dispose of."
As for the typical US home, most antiquated existing waste water treatment centers couldn't handle that volume of mixed food/water and would be overwhelmed. This is actually a concern expressed by other residents of our old condo building. People feared the sewer lines weren't large enough to accommodate everyone having a disposal.
Anyway, here at Humphrey House, we'll likely use a compost bin for most of the year and save the disposal for small pieces of food. And for when it is too darn cold to go out to a compost bin in winter!